Method for producing treatment agent for synthetic fibers, treatment agent for synthetic fibers, synthetic fibers, and method for producing synthetic fibers

ABSTRACT

The present invention addresses the problem of suitably suppressing fluffing during a spinning process. This method for producing a treatment agent for synthetic fibers, wherein the boron content in the nonvolatile content of the treatment agent for synthetic fibers as detected by ICP emission spectrometry is 200 ppm or less, comprises: an addition step wherein a (poly)oxyalkylene derivative is produced by adding an alkylene oxide to an alcohol in the presence of a catalyst that has a boron atom in each molecule; and a removal step wherein the catalyst is removed so that the boron content in the nonvolatile content of the treatment agent for synthetic fibers as detected by ICP emission spectrometry becomes 200 ppm or less.

TECHNICAL FIELD

The present invention relates to a method for producing a synthetic fiber treatment agent, a synthetic fiber treatment agent, a synthetic fiber, and a method for producing a synthetic fiber.

BACKGROUND ART

Carbon fibers are produced, for example, by performing a spinning step of spinning an acrylic resin into fibers to prepare a carbon fiber precursor that is synthetic fibers and a baking step of baking the synthetic fibers.

An acrylic fiber treatment agent that contains an amino-modified silicone and a polyoxyalkylene alkyl ether is disclosed in Patent Document 1.

PRIOR ART LITERATURE Patent Literature

-   Patent Document 1: International Publication No. WO 2017/169632

SUMMARY OF THE INVENTION Problems that the Invention is to Solve

Fluffing may occur on fibers in the spinning step, and suppression of fluffing in the spinning step is an issue.

The present invention has been made in view of such circumstances and an object thereof is to provide a method for producing a synthetic fiber treatment agent by which fluffing in a spinning step can be suppressed suitably. It is also an object of the present invention to provide a synthetic fiber treatment agent by which fluffing in a spinning step can be suppressed suitably, a synthetic fiber to which the synthetic fiber treatment agent is adhered, and a method for producing a synthetic fiber by using the synthetic fiber treatment agent.

Means for Solving the Problems

A method for producing a synthetic fiber treatment agent for solving the above problem is for producing a synthetic fiber treatment agent in which the content of boron detected by ICP emission spectrometry from the nonvolatile content of the synthetic fiber treatment agent is not more than 200 ppm and includes an addition step of adding an alkylene oxide to an alcohol under presence of a catalyst having a boron atom in its molecule to prepare a (poly)oxyalkylene derivative and a removal step of removing the catalyst such that the content of boron detected by ICP emission spectrometry from the nonvolatile content of the synthetic fiber treatment agent is not more than 200 ppm.

Regarding the method for producing a synthetic fiber treatment agent, it is preferable that in the removal step, the catalyst is removed such that the content of boron detected by ICP emission spectrometry from the nonvolatile content of the synthetic fiber treatment agent is not more than 40 ppm.

Regarding the method for producing a synthetic fiber treatment agent, the (poly)oxyalkylene derivative preferably includes a compound in which an alkylene oxide with 2 to 4 carbon atoms is added at a ratio of 1 to 30 moles in total to 1 mole of an alcohol.

Regarding the method for producing a synthetic fiber treatment agent, the alcohol is preferably that having an alkyl chain with 10 to 18 carbon atoms in its molecule.

Regarding the method for producing a synthetic fiber treatment agent, the alcohol is preferably that having an alkyl chain with 12 to 16 carbon atoms in its molecule.

Regarding the method for producing a synthetic fiber treatment agent, the alcohol is preferably a monohydric aliphatic alcohol having a hydroxy group at a β-position of an alkyl chain.

Regarding the method for producing a synthetic fiber treatment agent, it is preferable that the method further includes a mixing step of mixing in a smoothing agent.

Regarding the method for producing a synthetic fiber treatment agent, the smoothing agent preferably contains silicone.

Regarding the method for producing a synthetic fiber treatment agent, the smoothing agent preferably contains an amino-modified silicone.

Regarding the method for producing a synthetic fiber treatment agent, it is preferable that in the mixing step, if the sum of the contents of the (poly)oxyalkylene derivative and the smoothing agent is taken as 100 parts by mass, the smoothing agent is mixed such that the content of the (poly)oxyalkylene derivative is 10 to 70 parts by mass and the content of the smoothing agent is 90 to 30 parts by mass.

Regarding the method for producing a synthetic fiber treatment agent, the synthetic fiber is preferably a carbon fiber precursor.

A synthetic fiber treatment agent for solving the above problem contains a smoothing agent and a (poly)oxyalkylene derivative, and the content of boron detected by ICP emission spectrometry from the nonvolatile content of the treatment agent is not more than 200 ppm.

Regarding the synthetic fiber treatment agent, the content of boron is preferably not more than 40 ppm.

Regarding the synthetic fiber treatment agent, the (poly)oxyalkylene derivative preferably includes a compound in which an alkylene oxide with 2 to 4 carbon atoms is added at a ratio of 1 to 30 moles in total to 1 mole of an alcohol.

Regarding the synthetic fiber treatment agent, the alcohol preferably has an alkyl chain with 10 to 18 carbon atoms in its molecule.

Regarding the synthetic fiber treatment agent, the alcohol preferably has an alkyl chain with 12 to 16 carbon atoms in its molecule.

Regarding the synthetic fiber treatment agent, the alcohol is preferably a monohydric aliphatic alcohol having a hydroxy group at a β-position of an alkyl chain.

Regarding the synthetic fiber treatment agent, the smoothing agent preferably contains an amino-modified silicone.

Regarding the synthetic fiber treatment agent, it is preferable that if the sum of the contents of the (poly)oxyalkylene derivative and the smoothing agent is taken as 100 parts by mass, the content of the (poly)oxyalkylene derivative is 10 to 70 parts by mass and the content of the smoothing agent is 90 to 30 parts by mass.

Regarding the synthetic fiber treatment agent, the synthetic fiber is preferably a carbon fiber precursor.

A synthetic fiber for solving the above problem is a synthetic fiber to which the synthetic fiber treatment agent is adhered.

A method for producing a synthetic fiber for solving the above problem includes adhering the synthetic fiber treatment agent to fibers.

Effects of the Invention

The present invention succeeds in suitably suppressing fluffing in a spinning step.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of an apparatus for measuring smoothness.

MODES FOR CARRYING OUT THE INVENTION First Embodiment

A first embodiment that embodies a synthetic fiber treatment agent according to the present invention (also referred to hereinafter simply as treatment agent) will now be described.

The treatment agent of the present embodiment contains a smoothing agent and a (poly)oxyalkylene derivative. With the treatment agent, the content of boron detected by ICP emission spectrometry from the nonvolatile content of the treatment agent is not more than 200 ppm. By the content of boron in the treatment agent being not more than 200 ppm, fluffing in a spinning step can be suppressed suitably.

The content of boron detected by ICP emission spectrometry from the nonvolatile content of the treatment agent is preferably not more than 40 ppm and more preferably not more than 15 ppm. By the content of boron being not more than 40 ppm, the fluffing in the spinning step can be suppressed more suitably.

The content of boron detected by ICP emission spectrometry from the nonvolatile content of the treatment agent is also, for example, not less than 0.1 ppm, not less than 0.6 ppm, not less than 0.9 ppm, or not less than 2 ppm.

Examples of the (poly)oxyalkylene derivative include a compound in which an alkylene oxide is added to an alcohol or a carboxylic acid and an ether/ester compound in which an alkylene oxide is added to an ester compound of a carboxylic acid and a polyhydric alcohol. The alcohol or the carboxylic acid may be an aliphatic-based alcohol or carboxylic acid that is of a straight chain or has a branched chain or may be an aromatic-based alcohol or carboxylic acid. Alternatively, it may be a saturated alcohol or carboxylic acid or an unsaturated alcohol or carboxylic acid. Alternatively, it may be an alcohol or carboxylic acid that is monohydric or is dihydric or higher.

Specific examples of the (poly)oxyalkylene derivative include a compound in which 12 moles of ethylene oxide are added to 1 mole of 2-dodecanol, a compound in which 9 moles of ethylene oxide are added to 1 mole of 2-tetradecanol, a compound in which 5 moles of ethylene oxide are added to 1 mole of 2-dodecanol, a compound in which 9 moles of ethylene oxide are added to 1 mole of 2-dodecanol, a compound in which 30 moles of ethylene oxide are added to 1 mole of 2-dodecanol, a compound in which 9 moles of ethylene oxide are added to 1 mole of 2-tridecanol, a compound in which 12 moles of ethylene oxide are added to 1 mole of 2-tridecanol, a compound in which 9 moles of ethylene oxide are added to 1 mole of 2-decanol, a compound in which 9 moles of ethylene oxide are added to 1 mole of 2-octadecanol, a compound in which 5 moles of ethylene oxide are added to 1 mole of 2-nonanol, a compound in which 7 moles of ethylene oxide are added to 1 mole of 4-dodecanol, a compound in which 25 moles of ethylene oxide are added to 1 mole of 1-tetradecanol, a compound in which 5 moles of ethylene oxide are added to 1 mole of 2-pentadecanol, a compound in which 7 moles of ethylene oxide are added to 1 mole of 1-octanol, a compound in which 20 moles of ethylene oxide are added to 1 mole of 1-nonanol, a compound in which 9 moles of ethylene oxide are added to 1 mole of 1-dodecanol, and a compound in which 5 moles of ethylene oxide are added to 1 mole of 2-dodecanol.

One type of the (poly)oxyalkylene derivative may be used alone or two or more types thereof may be used in combination.

The (poly)oxyalkylene derivative is not restricted in particular in regard to the number of added moles of an alkylene oxide with 2 to 4 carbon atoms with respect to 1 mole of an alcohol, it preferably includes a compound in which an alkylene oxide with 2 to 4 carbon atoms is added at a ratio of 1 to 30 moles in total to 1 mole of an alcohol.

The alcohol preferably has an alkyl chain with 10 to 18 carbon atoms in its molecule and more preferably has an alkyl chain with 12 to 16 carbon atoms in its molecule.

The alcohol is preferably a monohydric aliphatic alcohol having a hydroxy group at a β-position of an alkyl chain. The monohydric aliphatic alcohol may be a saturated aliphatic alcohol or an unsaturated aliphatic alcohol. Alternatively, the monohydric aliphatic alcohol may be a straight chain aliphatic alcohol or an aliphatic alcohol having a branched chain.

By using the monohydric aliphatic alcohol having the hydroxy group at the β-position of the alkyl chain, a wetting property of the treatment agent with respect to a synthetic fiber is improved as will be described below.

Specific examples of the alkylene oxide with 2 to 4 carbon atoms include ethylene oxide, propylene oxide, and butylene oxide. Among these, ethylene oxide is preferable. The polymerization sequence is not restricted in particular and may be either a block adduct or a random adduct.

Examples of the smoothing agent contained in the treatment agent of the present embodiment include a silicone and an ester.

The silicone used as the smoothing agent is not restricted in particular, and examples thereof include a dimethyl silicone, phenyl-modified silicone, amino-modified silicone, amide-modified silicone, polyether-modified silicone, aminopolyether-modified silicone, alkyl-modified silicone, alkyl aralkyl-modified silicone, alkyl polyether-modified silicone, ester-modified silicone, epoxy-modified silicone, carbinol-modified silicone, and mercapto-modified silicone.

Among the above, it is preferable for an amino-modified silicone to be contained.

By the smoothing agent containing an amino-modified silicone, smoothness of the treatment agent can be improved as will be described below.

The ester used as the smoothing agent is not restricted in particular, and examples thereof include (1) an ester compound of an aliphatic monoalcohol and an aliphatic monocarboxylic acid, such as octyl palmitate, oleyl laurate, oleyl oleate, and isotetracosyl oleate, (2) an ester compound of an aliphatic polyhydric alcohol and an aliphatic monocarboxylic acid, such as 1,6-hexanediol didecanoate, glycerin trioleate, trimethylolpropane trilaurate, and pentaerythritol tetraoctanoate, (3) an ester compound of an aliphatic monoalcohol and an aliphatic polycarboxylic acid, such as dioleyl azelate, dioleyl thiodipropionate, diisocetyl thiodipropionate, and diisostearyl thiodipropionate, (4) an ester compound of an aromatic monoalcohol and an aliphatic monocarboxylic acid, such as benzyl oleate and benzyl laurate, (5) a complete ester compound of an aromatic polyhydric alcohol and an aliphatic monocarboxylic acid, such as bisphenol A dilaurate and dilaurate of an alkylene oxide adduct of bisphenol A, (6) a complete ester compound of an aliphatic monoalcohol and an aromatic polycarboxylic acid, such as bis-2-ethylhexylphthalate, diisostearyl isophthalate, and trioctyl trimellitate, and (7) natural oils and fats, such as coconut oil, rapeseed oil, sunflower oil, soybean oil, castor oil, sesame oil, fish oil, and beef tallow. Besides the above, a known smoothing agent that is adopted in synthetic fiber treatment agents may be used.

Specific examples of the smoothing agent include an amino-modified silicone with a kinematic viscosity at 25° C. of 650 mm²/s and an amino equivalent weight of 1,800 g/mol, an amino-modified silicone with a kinematic viscosity at 25° C. of 90 mm²/s and an amino equivalent weight of 5,000 g/mol, an amino-modified silicone with a kinematic viscosity at 25° C. of 4,500 mm²/s and an amino equivalent weight of 1,200 g/mol, an amino-modified silicone with a kinematic viscosity at 25° C. of 40 mm²/s and an amino equivalent weight of 1,800 g/mol, an amino-modified silicone with a kinematic viscosity at 25° C. of 8,000 mm²/s and an amino equivalent weight of 1,000 g/mol, a polyether-modified silicone with a kinematic viscosity at 25° C. of 500 mm²/s and with ethylene oxide/propylene oxide=100/0 and mass ratio of silicone/polyether=50/50, a polyether-modified silicone with a kinematic viscosity at 25° C. of 1,700 mm²/s and with ethylene oxide/propylene oxide=40/60 and mass ratio of silicone/polyether=20/80, a dimethyl silicone with a kinematic viscosity at 25° C. of 10,000 mm²/s, thiodipropionic acid di(n-dodecyl) ester, and a dilauryl ester of a 2 mole ethylene oxide adduct of bisphenol A.

One type of the smoothing agent may be used alone or two or more types thereof may be used in combination.

The contents of the (poly)oxyalkylene derivative and the smoothing agent are not restricted. If the sum of the contents of the (poly)oxyalkylene derivative and the smoothing agent is taken as 100 parts by mass, it is preferable for the treatment agent to contain the (poly)oxyalkylene derivative at a ratio of 10 to 70 parts by mass and the smoothing agent at a ratio of 90 to 30 parts by mass. The treatment agent more preferably contains the (poly)oxyalkylene derivative at a ratio of 20 to 60 parts by mass and the smoothing agent at a ratio of 80 to 40 parts by mass.

Second Embodiment

A second embodiment that embodies a method for producing a treatment agent according to the present invention will now be described. Differences with respect to the first embodiment will mainly be described.

The method for producing a treatment agent includes an addition step of adding the alkylene oxide to the alcohol under presence of a catalyst having a boron atom in its molecule to prepare the (poly)oxyalkylene derivative and a removal step of removing the catalyst such that the content of boron detected by ICP emission spectrometry from the nonvolatile content of the treatment agent is not more than 200 ppm.

The catalyst having a boron atom in its molecule is not restricted in particular and can be an acid catalyst, such as boron trifluoride or a complex thereof.

As an example of the addition step, a low number of moles, for example, 1 to 5 moles of ethylene oxide are made to react with the alcohol using an acid catalyst, such as boron trifluoride or a complex thereof, and the catalyst is removed to obtain a low mole ethoxylate compound. Next, ethylene oxide is made to react with the obtained low mole ethoxylate compound under presence of an alkali catalyst, such as sodium hydroxide, potassium hydroxide, or sodium alkoxide, and then the catalyst is removed.

The method for removing the catalyst from a liquid that has undergone the addition step is not restricted in particular, and a known method can be used. Examples of the method for removing the catalyst include a method of using diatomaceous earth to filter the liquid and separate the catalyst, and a method of using an inorganic synthetic adsorbent to adsorb and remove the catalyst from the liquid.

The ICP emission spectrometry can be performed, for example, by the following procedures. First, solutions of known concentrations of boron (for example, a 0.5 ppm solution and a 1 ppm solution) are prepared in advance and measured with an ICP emission spectrometer to prepare a calibration curve. Next, the treatment agent that has undergone the removal step is measured with the ICP emission spectrometer and the content of boron contained in the nonvolatile content of the treatment agent is measured using the calibration curve prepared above.

The method for producing a treatment agent of the present embodiment preferably include a mixing step of mixing in the smoothing agent. In the mixing step, the smoothing agent is preferably mixed with the (poly)oxyalkylene derivative such as to achieve the contents of the (poly)oxyalkylene derivative and the smoothing agent specified for in the first embodiment.

Third Embodiment

A third embodiment that embodies a synthetic fiber according to the present invention will now be described. The synthetic fiber of the present embodiment has the treatment agent of the first embodiment adhered thereto. The synthetic fiber is no restricted in particular, and specific examples thereof include (1) polyethylene terephthalate, polypropylene terephthalate, polylactic acid ester, and other polyester fibers, (2) nylon 6, nylon 66, and other polyamide fibers, (3) polyacrylic, modacrylic, and other polyacrylic fibers, (4) polyethylene, polypropylene, and other polyolefin fibers, (5) cellulose fibers, and (6) lignin fibers. As the synthetic fibers, a carbon fiber precursor is preferable that is made of resin and becomes carbon fibers by undergoing a carbonization step to be described below. The resin constituting the carbon fiber precursor is not restricted in particular, and specific examples thereof include an acrylic resin, polyethylene resin, phenol resin, cellulose resin, lignin resin, and pitch.

The amount of the treatment agent of the first embodiment to be adhered to the synthetic fiber is not restricted in particular, and the treatment agent (not including solvent) is adhered such as to be preferably 0.1% to 2% by mass and more preferably 0.3% to 1.2% by mass with respect to the synthetic fiber.

Fourth Embodiment

A fourth embodiment that embodies a method for producing a synthetic fiber according to the present invention will now be described. The method for producing a synthetic fiber of the present embodiment includes adhering the treatment agent of the first embodiment to a fiber.

Examples of the form of the treatment agent of the first embodiment when adhering the treatment agent to the fiber include an organic solvent solution and an aqueous liquid.

The method for adhering the treatment agent to the synthetic fiber may be a method of using, for example, an aqueous liquid containing the treatment agent of the first embodiment and water or using a further diluted aqueous solution to adhere by a known method such as an immersion method, a spray method, a roller method, or a guide oiling method using a metering pump.

A method for producing a carbon fiber using the synthetic fiber of the present embodiment will now be described.

The method for producing a carbon fiber preferably includes the following Steps 1 to 3.

Step 1: a spinning step of spinning the synthetic fibers and adhering the treatment agent of the first embodiment to the synthetic fiber.

Step 2: a flame-resisting treatment step of converting the synthetic fiber obtained in Step 1 to a flame-resistant fiber in an oxidizing atmosphere of 200° C. to 300° C. and preferably 230° C. to 270° C.

Step 3: a carbonization step of carbonizing the flame-resistant fiber obtained in Step 2 in an inert atmosphere of 300° C. to 2,000° C. and preferably 300° C. to 1,300° C.

It is deemed that a baking step is constituted of Step 2 and Step 3 above.

The spinning step preferably further includes a wet spinning step of dissolving a resin in a solvent and spinning it into a fiber, a dry densification step of drying and densifying the wet-spun synthetic fiber, and a drawing step of drawing the dry densified synthetic fiber.

Although a temperature of the dry densification step is not restricted in particular, the synthetic fiber that has undergone the wet spinning step is preferably heated, for example, at 70° C. to 200° C. Although a timing at which the treatment agent is adhered to the synthetic fiber is not restricted in particular, it is preferably between the wet spinning step and the dry densification step.

The oxidizing atmosphere in the flame-resisting treatment step is not restricted in particular and may be, for example, an air atmosphere.

The inert atmosphere in the carbonization step is not restricted in particular and may be, for example, a nitrogen atmosphere, an argon atmosphere, or a vacuum atmosphere.

The following effects can be obtained by the treatment agent, the method for producing the same, the synthetic fiber, and the method for producing the same of the embodiments.

(1) The treatment agent of the embodiments contains the smoothing agent and the (poly)oxyalkylene derivative, and the content of boron detected from the nonvolatile content of the treatment agent by ICP emission spectrometry is of specified value. This allows suppression of fluffing of fibers that have undergone the spinning step. In addition, smoothness of the fibers that have undergone the spinning step can be improved. Further, bundling property of the flame-resistant fibers that have undergone the flame-resisting treatment step can be improved.

(2) By the treatment agent of the embodiments, the wetting property with respect to the synthetic fibers is improved and therefore, the treatment agent can be adhered to the synthetic fibers more uniformly.

(3) The treatment agent is adhered to a synthetic fiber between the wet spinning step and the dry densification step. Therefore, fluffing can be suppressed suitably especially in the dry densification step within the spinning step.

The above-described embodiments can be modified as follows. The above-described embodiments and the following modifications can be implemented upon being combined with each other within a range that is not technically inconsistent.

In the embodiments, the removal step of the catalyst having a boron atom may be performed immediately after the addition step, in the middle of the addition step, or after mixing in another ingredient.

In the embodiments, for example, the synthetic fiber may be a fiber on which the baking step is not performed.

Stabilizers, antistatic agents, electrostatic preventing agents, binders, antioxidant agents, ultraviolet absorbers, and other ingredients that are ordinarily used in treatment agents or aqueous liquids for quality maintenance of the treatment agents or the aqueous liquids may further be blended in the treatment agent or the aqueous liquid of the embodiments within a range that does not impair the effects of the present invention.

EXAMPLES

Examples will now be given below to describe the features and effects of the present invention more specifically, but the present invention is not restricted to these examples. In the following description of examples and comparative examples, parts means parts by mass and % means % by mass.

Experimental Part 1 (Preparation of Synthetic Fiber Treatment Agents)

Example 1

First, as the addition step, 186 parts of 2-dodecanol and 0.5 parts of boron trifluoride were added into an autoclave and after replacing the atmosphere with nitrogen gas, 132 parts of ethylene oxide were added gradually at 150° C. to perform etherification.

Next, as the removal step of the catalyst, 5 parts of an anion exchange resin were added to the liquid in which the etherification was performed and stirring at room temperature was performed for 30 minutes. Thereafter, the liquid was transferred to a filter precoated with diatomaceous earth and the anion exchange resin that adsorbed the boron trifluoride catalyst was removed to prepare a 3 mole ethylene oxide adduct of 2-dodecanol.

Further, 318 parts of the obtained 3 mole ethylene oxide adduct of 2-dodecanol and 0.5 parts of sodium hydroxide were added into an autoclave and after replacing the atmosphere with nitrogen gas, 396 parts of ethylene oxide were added gradually at 150° C. to perform etherification.

Further, 10 parts of an inorganic synthetic adsorbent were added to the liquid in which the etherification was performed and stirring at 80° C. was performed for 30 minutes. Thereafter, the liquid was transferred to a filter precoated with diatomaceous earth and the inorganic synthetic adsorbent that adsorbed the sodium hydroxide catalyst was removed to prepare a (poly)oxyalkylene derivative (A-1) shown in Table 1.

The respective ingredients shown in Table 1 were used and added to a beaker such that blending ratios are 30 parts of the (poly)oxyalkylene derivative (A-1) and 70 parts of a smoothing agent (B-1). These were mixed well by stirring. While continuing to stir, ion exchanged water was added gradually to achieve a solids concentration of 25% and thereby prepare a 25% aqueous liquid of a synthetic fiber treatment agent of Example 1.

Examples 2 to 23 and Comparative Examples 1 to 3

Respective synthetic fiber treatment agents of Examples 2 to 23 and Comparative Examples 1 to 4 were prepared using the respective ingredients shown in Table 1 and in accordance with the same procedure as Example 1.

For the treatment agent of each example, the type and content of the (poly)oxyalkylene derivative, the type and content of the smoothing agent, and the content of boron in the treatment agent are as respectively indicated in the “(A) Polyoxyalkylene derivative” column, the “(B) Smoothing agent” column, and the “B content in treatment agent (ppm)” column of Table 1.

TABLE 1 (A) (B) Evaluation (Poly)oxyalkylene Smoothing B content Flame- derivative agent in treatment resistant Parts Parts agent Spinning bundling Smooth- Wetting Symbol by mass Symbol by mass (ppm) fluff property ness property Example 1 A-1 30 B-1 70 0.9 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 2 A-1 30 B-2 70 0.9 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 3 A-1 30 B-3 70 0.9 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 4 A-1 30 B-4 70 0.9 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 5 A-2 65 B-2 35 2.6 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 6 A-3 20 B-3 80 0.6 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 7 A-4 30 B-4 70 2.7 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 8 A-5 35 B-5 65 3.2 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 9 A-6 60 B-1 40 13 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 10 A-7 10 B-1 90 0.1 ∘∘∘ ∘∘ ∘∘∘ ∘∘ Example 11 A-2 50 B-1 25 2 ∘∘∘ ∘∘ ∘∘∘ ∘∘ B-2 25 Example 12 A-1 30 B-6 70 0.9 ∘∘∘ ∘∘ ∘∘ ∘∘ Example 13 A-1 30 B-7 70 0.9 ∘∘∘ ∘∘ ∘∘ ∘∘ Example 14 A-1 30 B-8 70 0.9 ∘∘∘ ∘∘ ∘∘ ∘∘ Example 15 A-1 30 B-9 70 0.9 ∘∘∘ ∘∘ ∘ ∘∘ Example 16 A-1 30 B-10 70 0.9 ∘∘∘ ∘∘ ∘ ∘∘ Example 17 A-8 30 B-1 70 2.7 ∘∘ ∘∘ ∘∘∘ ∘∘ Example 18 A-9 30 B-1 70 2.4 ∘∘ ∘∘ ∘∘∘ ∘∘ Example 19 A-10 30 B-1 70 2.7 ∘∘ ∘ ∘∘∘ ∘∘ Example 20 A-11 30 B-1 70 3.6 ∘∘ ∘∘ ∘∘∘ ∘ Example 21 A-12 30 B-9 70 2.7 ∘∘ ∘∘ ∘ ∘ Example 22 A-13 30 B-1 70 65 ∘ ∘∘ ∘ ∘∘ Example 23 A-14 40 B-10 60 78 ∘ ∘ ∘ ∘ Comparative a-1 30 B-9 70 396 x x x x Example 1 Comparative a-2 30 B-9 70 464 x ∘ x x Example 2 Comparative a-3 30 B-10 70 430 x ∘ x ∘ Example 3

Details of the respective ingredients A-1 to A-14, a-1 to a-3, and B-1 to B-10 indicated in the symbol columns of Table 1 are as follows.

((Poly)Oxyalkylene Derivatives)

A-1: compound in which 12 moles of ethylene oxide are added to 1 mole of 2-dodecanol

A-2: compound in which 9 moles of ethylene oxide are added to 1 mole of 2-tetradecanol

A-3: compound in which 5 moles of ethylene oxide are added to 1 mole of 2-dodecanol

A-4: compound in which 9 moles of ethylene oxide are added to 1 mole of 2-dodecanol

A-5: compound in which 30 moles of ethylene oxide are added to 1 mole of 2-dodecanol

A-6: compound in which 9 moles of ethylene oxide are added to 1 mole of 2-tridecanol

A-7: compound in which 12 moles of ethylene oxide are added to 1 mole of 2-tridecanol

A-8: compound in which 9 moles of ethylene oxide are added to 1 mole of 2-decanol

A-9: compound in which 9 moles of ethylene oxide are added to 1 mole of 2-octadecanol

A-10: compound in which 5 moles of ethylene oxide are added to 1 mole of 2-nonanol

A-11: compound in which 7 moles of ethylene oxide are added to 1 mole of 4-dodecanol

A-12: compound in which 25 moles of ethylene oxide are added to 1 mole of 1-tetradecanol

A-13: compound in which 5 moles of ethylene oxide are added to 1 mole of 2-pentadecanol

A-14: compound in which 7 moles of ethylene oxide are added to 1 mole of 1-octanol

a-1: compound in which 20 moles of ethylene oxide are added to 1 mole of 1-nonanol

a-2: compound in which 9 moles of ethylene oxide are added to 1 mole of 1-dodecanol

a-3: compound in which 5 moles of ethylene oxide are added to 1 mole of 2-dodecanol

For each of the above (poly)oxyalkylene derivatives, the type of (poly)oxyalkylene derivative used, the number of carbon atoms of the alcohol, the position of the hydroxy group in the alkyl chain, and the boron content of the (poly)oxyalkylene derivative are respectively indicated in the “(A) (Poly)oxyalkylene derivative” column, the “Number of carbon atoms of monohydric aliphatic alcohol” column, the “Position of hydroxy group” column, and the “B content (ppm)” column of Table 2.

TABLE 2 Number of Position carbon atoms of B (A) of monohydric hydroxy content Symbol (Poly)oxyalkylene derivative aliphatic alcohol group (ppm) A-1 Compound in which 12 moles of ethylene 12 β-position 3 oxide are added to 1 mole of 2-dodecanol A-2 Compound in which 9 moles of ethylene 14 β-position 4 oxide are added to 1 mole of 2-tetradecanol A-3 Compound in which 5 moles of ethylene 12 β-position 3 oxide are added to 1 mole of 2-dodecanol A-4 Compound in which 9 moles of ethylene 12 β-position 9 oxide are added to 1 mole of 2-dodecanol A-5 Compound in which 30 moles of ethylene 12 β-position 9 oxide are added to 1 mole of 2-dodecanol A-6 Compound in which 9 moles of ethylene 13 β-position 21 oxide are added to 1 mole of 2-tridecanol A-7 Compound in which 12 moles of ethylene 13 β-position 1 oxide are added to 1 mole of 2-tridecanol A-8 Compound in which 9 moles of ethylene 10 β-position 9 oxide are added to 1 mole of 2-decanol A-9 Compound in which 9 moles of ethylene 18 β-position 8 oxide are added to 1 mole of 2-octadecanol A-10 Compound in which 5 moles of ethylene 9 β-position 9 oxide are added to 1 mole of 2-nonanol A-11 Compound in which 7 moles of ethylene 12 δ-position 12 oxide are added to 1 mole of 4-dodecanol A-12 Compound in which 25 moles of ethylene 14 α-position 9 oxide are added to 1 mole of 1-tetradecanol A-13 Compound in which 5 moles of ethylene 15 β-position 216 oxide are added to 1 mole of 2-pentadecanol A-14 Compound in which 7 moles of ethylene 8 α-position 194 oxide are added to 1 mole of 1-octanol a-1 Compound in which 20 moles of ethylene 9 α-position 1320 oxide are added to 1 mole of 1-nonanol a-2 Compound in which 9 moles of ethylene 12 α-position 1547 oxide are added to 1 mole of 1-dodecanol a-3 Compound in which 5 moles of ethylene 12 β-position 1432 oxide are added to 1 mole of 2-dodecanol

In Table 2, the differences among the boron contents in the respective (poly)oxyalkylene derivatives are based on differences in duration of removal of the anionic exchange resin that adsorbed the boron trifluoride catalyst by the filter precoated with diatomaceous earth in the removal step of the catalyst described above. That is, the longer the duration of removal of the anionic exchange resin that adsorbed the boron trifluoride catalyst by the filter precoated with diatomaceous earth, the less the boron content in the (poly)oxyalkylene derivative.

(Smoothing Agents)

B-1: amino-modified silicone with a kinematic viscosity at 25° C. of 650 mm²/s and an amino equivalent weight of 1,800 g/mol

B-2: amino-modified silicone with a kinematic viscosity at 25° C. of 90 mm²/s and an amino equivalent weight of 5,000 g/mol

B-3: amino-modified silicone with a kinematic viscosity at 25° C. of 4,500 mm²/s and an amino equivalent weight of 1,200 g/mol

B-4: amino-modified silicone with a kinematic viscosity at 25° C. of 40 mm²/s and an amino equivalent weight of 1,800 g/mol

B-5: amino-modified silicone with a kinematic viscosity at 25° C. of 8,000 mm²/s and an amino equivalent weight of 1,000 g/mol

B-6: polyether-modified silicone with a kinematic viscosity at 25° C. of 500 mm²/s and with ethylene oxide/propylene oxide=100/0 and mass ratio of silicone/polyether=50/50

B-7: polyether-modified silicone with a kinematic viscosity at 25° C. of 1,700 mm²/s and with ethylene oxide/propylene oxide=40/60 and mass ratio of silicone/polyether=20/80

B-8: dimethyl silicone with a kinematic viscosity at 25° C. of 10,000 mm²/s

B-9: thiodipropionic acid di(n-dodecyl) ester

B-10: dilauryl ester of a 2 mole ethylene oxide adduct of bisphenol A

Experimental Part 2 (Production of Synthetic Fibers and Carbon Fibers)

Synthetic fibers and carbon fibers were produced using the aqueous liquids of synthetic fiber treatment agents prepared in Experimental Part 1.

First, as Step 1, an acrylic resin was wet spun as synthetic fibers. Specifically, a copolymer of 1.80 limiting viscosity constituted of 95% by mass acrylonitrile, 3.5% by mass methyl acrylate, and 1.5% by mass methacrylic acid was dissolved in dimethylacetamide (DMAC) to prepare a spinning dope with a polymer concentration of 21.0% by mass and a viscosity at 60° C. of 500 poise. The spinning dope was discharged at a draft ratio of 0.8 from a spinneret with 12,000 holes of 0.075 mm hole diameter (inner diameter) into a coagulation bath of a 70% by mass aqueous solution of DMAC maintained at a spinning bath temperature of 35° C.

The coagulated yarn was drawn by 5 times at the same time as being desolvated in a rinse tank to prepare acrylic fiber strands (raw material fibers) in a water-swollen state. To these acrylic fiber strands, the synthetic fiber treatment agents prepared in Experimental Part 1 were each applied such that a solids adhesion amount would be 1% by mass (not including the solvent). Application of each synthetic fiber treatment agent was performed by an immersion method using a 4% ion exchanged water solution of the synthetic fiber treatment agent. Thereafter, the acrylic fiber strands were subject to dry densification by a heating roller set at 130° C., further subject to drawing by 1.7 times between heating rollers set at 170° C., and thereafter wound around a spool using a winding device (also referred to hereinafter as winder).

Next, as Step 2, yarns were unwound from the wound synthetic fibers and, after being subject to flame-resisting treatment for 1 hour under an air atmosphere in a flame-resisting treatment furnace having a temperature gradient of 230° C. to 270° C., were wound around a spool to obtain flame-resistant yarns (flame-resistant fibers).

Next, as Step 3, yarns were unwound from the wound flame-resistant yarns and, after conversion to carbon fibers by baking under a nitrogen atmosphere in a carbonizing furnace having a temperature gradient of 300° C. to 1300° C., were wound around a spool to obtain the carbon fibers.

Experimental Part 3 (Evaluation)

Regarding each of the treatment agents of Examples 1 to 23 and Comparative Examples 1 to 3, the fluffing in the spinning step of the synthetic fibers, the bundling property of the fire-resistant fibers, the smoothness of the synthetic fibers, and the wetting property with respect to the synthetic fibers were evaluated. Procedures of the respective tests are described below. The test results are shown in the “Spinning fluff,” “Flame-resistant bundling property,” “Smoothness,” and “Wetting property” columns of Table 1.

(Spinning Fluff)

The number of fluffs per hour measured by a fluff counter installed immediately in front of the winding device for winding the synthetic fibers in Step 1 of Experimental Part 2 was evaluated based on the following criteria.

Evaluation Criteria of Fluffing

◯◯◯ (excellent): The number of fluffs was 0 to 2.

◯◯ (satisfactory): The number of fluffs was 3 to 5.

◯ (fair): The number of fluffs was 6 to 10.

x (poor): The number of fluffs was 11 or more.

(Flame-Resistant Bundling Property)

With the flame-resistant fibers on which the flame-resisting treatment was performed in Step 2 of Experimental Part 2, the bundling state of the flame-resisting yarns before winding was visually observed and the flame-resistant bundling property was evaluated based on the following criteria.

Evaluation criteria of flame-resistant bundling property

◯◯ (satisfactory): Bundling is achieved and a tow width is constant.

◯ (fair): Although bundling is achieved, the tow width is not constant.

x (poor): There are spaces inside the fiber bundles and bundling is not achieved.

(Smoothness)

As a device for measuring smoothness, Autograph ABS-1kNX (tensile tester) manufactured by Shimadzu Corporation was used.

As shown in FIG. 1 , the synthetic fiber with the treatment agent adhered (also referred to hereinafter as test yarn 1) was fixed at one end to a gripping tool 2 of the autograph and successively passed along a free roller 3, a chrome-plated textured pin 4, and a free roller 5 and a weight 6 of 50 g was fixed to the other end of the test yarn 1. A drive shaft 4 a that the test yarn 1 contacts at the chrome-plated textured pin 4 is 1 cm in diameter and 2S in surface roughness. An angle formed by a direction in which the test yarn 1 extends between the chrome-plated textured pin 4 and the free roller 5 with respect to a direction in which the test yarn 1 extends between the free roller 3 and the chrome-plated textured pin 4 was set to 90°. In this state and under conditions of 25° C. and 60% RH, the drive shaft 4 a of the chrome-plated textured pin 4 was put in a state of being rotated at a speed of 100 m/minute circumferential speed in a direction in which tension is applied to the autograph and the tension was measured by the autograph every 0.1 seconds for 30 seconds. An average value (N) of the tension during this time was determined and evaluated based on the following criteria.

◯◯◯ (excellent): The average value of tension is less than 2N.

◯◯ (satisfactory): The average value of tension is not less than 2N but less than 3N.

◯ (fair): The average value of tension is not less than 3N but less than 4N.

x (poor): The average value of tension is not less than 4N.

(Wetting Property)

With each synthetic fiber treatment agent, a 4% ion exchanged water solution of the effective ingredients (a solution with the portion other than ion exchanged water being the effective ingredients) was prepared and after dropping 0.1 g thereof onto an acrylic plate, a maximum diameter (mm) after 1 minute was measured and evaluated based on the following criteria.

◯◯ (satisfactory): The maximum diameter is 12 mm or more.

◯ (fair): The maximum diameter is not less than 10 mm but less than 12 mm.

x (poor): The maximum diameter is less than 10 mm.

Based on the results of Table 1, the present invention succeeds in suitably suppressing fluffing in the spinning step of the synthetic fibers. In addition, the bundling property of the fire-resistant fibers and the smoothness of the synthetic fibers can be improved. Further, by the treatment agent of the present invention, the wetting property with respect to the synthetic fibers is improved. 

1. A method for producing a synthetic fiber treatment agent, the content of boron detected by ICP emission spectrometry from the nonvolatile content of the synthetic fiber treatment agent being not more than 200 ppm, the method comprising: an addition step of adding an alkylene oxide to an alcohol under presence of a catalyst having a boron atom in its molecule to prepare a (poly)oxyalkylene derivative, and a removal step of removing the catalyst such that the content of boron detected by ICP emission spectrometry from the nonvolatile content of the synthetic fiber treatment agent is not more than 200 ppm.
 2. The method for producing a synthetic fiber treatment agent according to claim 1, wherein in the removal step, the catalyst is removed such that the content of boron detected by ICP emission spectrometry from the nonvolatile content of the synthetic fiber treatment agent is not more than 40 ppm.
 3. The method for producing a synthetic fiber treatment agent according to claim 1, wherein the (poly)oxyalkylene derivative includes a compound in which an alkylene oxide with 2 to 4 carbon atoms is added at a ratio of 1 to 30 moles in total to 1 mole of an alcohol.
 4. The method for producing a synthetic fiber treatment agent according to claim 1, wherein the alcohol has an alkyl chain with 10 to 18 carbon atoms in its molecule.
 5. The method for producing a synthetic fiber treatment agent according to claim 1, wherein the alcohol has an alkyl chain with 12 to 16 carbon atoms in its molecule.
 6. The method for producing a synthetic fiber treatment agent according to claim 4, wherein the alcohol is a monohydric aliphatic alcohol having a hydroxy group at a β-position of an alkyl chain.
 7. The method for producing a synthetic fiber treatment agent according to claim 1, further comprising a mixing step of mixing in a smoothing agent.
 8. The method for producing a synthetic fiber treatment agent according to claim 7, wherein the smoothing agent contains silicone.
 9. The method for producing a synthetic fiber treatment agent according to claim 7, wherein the smoothing agent contains an amino-modified silicone.
 10. The method for producing a synthetic fiber treatment agent according to claim 7, wherein in the mixing step, if the sum of the contents of the (poly)oxyalkylene derivative and the smoothing agent is taken as 100 parts by mass, the smoothing agent is mixed such that the content of the (poly)oxyalkylene derivative is 10 to 70 parts by mass and the content of the smoothing agent is 90 to 30 parts by mass.
 11. The method for producing a synthetic fiber treatment agent according to claim 1, wherein the synthetic fiber is a carbon fiber precursor.
 12. A synthetic fiber treatment agent comprising a smoothing agent and a (poly)oxyalkylene derivative, wherein the content of boron detected by ICP emission spectrometry from the nonvolatile content of the treatment agent is not less than 0.1 ppm and not more than 200 ppm.
 13. The synthetic fiber treatment agent according to claim 12, wherein the content of boron is not more than 40 ppm.
 14. The synthetic fiber treatment agent according to claim 12, wherein the (poly)oxyalkylene derivative includes a compound in which an alkylene oxide with 2 to 4 carbon atoms is added at a ratio of 1 to 30 moles in total to 1 mole of an alcohol.
 15. The synthetic fiber treatment agent according to claim 14, wherein the alcohol has an alkyl chain with 10 to 18 carbon atoms in its molecule.
 16. The synthetic fiber treatment agent according to claim 14, wherein the alcohol has an alkyl chain with 12 to 16 carbon atoms in its molecule.
 17. The synthetic fiber treatment agent according to claim 15, wherein the alcohol is a monohydric aliphatic alcohol having a hydroxy group at a β-position of an alkyl chain.
 18. The synthetic fiber treatment agent according to claim 12, wherein the smoothing agent contains an amino-modified silicone.
 19. The synthetic fiber treatment agent according to claim 12, wherein if the sum of the contents of the (poly)oxyalkylene derivative and the smoothing agent is taken as 100 parts by mass, content of the (poly)oxyalkylene derivative is 10 to 70 parts by mass and the content of the smoothing agent is 90 to 30 parts by mass.
 20. The synthetic fiber treatment agent according to claim 12, wherein the synthetic fiber is a carbon fiber precursor.
 21. A synthetic fiber to which the synthetic fiber treatment agent according to claim 12 is adhered.
 22. A method for producing a synthetic fiber including adhering the synthetic fiber treatment agent according to claim 12 to a fiber. 